PREVERO Report Summary

CFD results of cavitating flows

CFD simulation studies in the first stage included basic cavitating flow calculations on the geometry from the University of Ljubljana to test the basic capability of the applied CFD tool AVL FIRE. The results were compared to the measured data.

The geometries investigated at other partners' (LEGI, TU Graz, BOSCH) have been investigated in preliminary studies. In all of the simulations it was important to explore the limits of the code to define the software requirements of the new numerical cavitation model, developed and implemented into FIRE later on by AVL.

Cavitation phenomena itself was predicted successfully; the limit was the quantification of the collapsing bubbles which are the driving force of the erosion process.

An advanced cavitation model was implemented in the FIRE code in order to quantify the number of collapsing bubbles, which cause erosion damage. An advanced turbulence model (k-zeta-f turb. model previously available in FIRE for single-phase applications) was adopted for cavitating flows and validated against experimental results obtained by University of Ljubljana LFDT.

The experimental results on A-throttle geometry were verified by CRF using the CFD code FIRE, the results were in good agreement.

BOSCH used 2 CFD codes to validate their own experimental results. Physical flow chracteristics were identified. It can be concluded that distribution and the position of the predicted and the measured volume fraction was in acceptable agreement. Shear layer induced cavitation behind the throttle is difficult or even impossible to catch with RANS based two-phase models. Small variations of the experimental geometry lead to significant changes of the flow field and can not be represented in the simulation model.